forest regeneration

regeneration

the act of establishing young trees naturally or artificially

regeneration period

• greatest stand plasticity → stand trajectory

artificial regeneration

an age class created by direct seeding or by planting seedlings or cuttings

stand initiation stage

• initial cohort of trees take advantage of available growing space

• species composition

species composition

• source of regeneration

• growth rates

• severity of disturbances

regeneration mechanisms

• seeds

• root and stump sprouts

• advanced regeneration

seeds

• RTD

• most common

• buried or imported

• production, sporadic for most species

• have stratification (dormancy) requirement

• some have scarification requirement

root and stump sprouts

• RTD

• advantage of large, established root system

• the larger the stump, or the higher the stump, the lower the probability of a successful sprout

advanced regeneration

• RTD

• seedlings that are present before the disturbance occurs

high forests

• stand origin

• seed origin

• sexual reproduction

• conifer and hardwoods

low forests

• stand origin

• vegetative origin

• asexual reproduction

• mainly hardwoods (sprouts), few conifers (layering)

moisture, temperature, and light

the three big gradients

microsite

• stand and trees are disturbed, BUT

• germination occurs on a much smaller spatial scale

• conditions that govern successful germination are different from those that govern tree growth and stand development

moisture

• closed canopy- water loss occurs mostly from tree transpiration during photosynthesis

• large forest opening- water loss occurs mostly from evaporation

temperature

• surface and soil temperatures increase due to lack of shade

• the rough land surface impedes heat transfer from surface to air

• surfaces heat up quickly during the day

• surfaces cool quickly during the night

• both extremes may be lethal to germinating plants

• soil temps may be > than air temps

light quantity

• light at the forest floor under a closed canopy is typically <5% of the light at the top of the canopy

• consider the effects of latitude and topography

• differences in light quality

biotic

• competition

• facilitation: nurse crops

• damaging agents

masting

• seed supply

• good seed years separated by intervals of poor seed production

• predator satiation

• many factors

seed storage

• soil seed bank

• cone serotiny

wind dispersed

• seed rain

• depends on seed size

• most seeds near parent

animal dispersed

• predator satiation

• eg dispersed by birds and mammals

breaking dormancy

• seed coat: scarification

• moisture

• temperature: stratification

organic matter seed beds

• variable moisture environment

• reduced surface area contact for roots

mineral soil seed beds

• stabler soil moisture supply

• greater surface area contact for roots

• preferred by most species

red oak challenges

• acorn predation

• fire dependent species

• fire suppression and mesophication of the east

mechanism of suckering

hormones related to the apical meristem usually keep adventitious buds dormant

sprouting from buds

• damage to apical meristem removes apical dominance

• adventitious buds can arise from shoot and roots

black spruce layering

• layering: covered lower branches develop roots and shoots

• poorly drained and undrained areas

• organic soils: deep, very acidic peat